MS ABI: Consider alignment attributes on typedefs for layout

The MS ABI has a notion of 'required alignment' for fields; this
alignment supercedes pragma pack directives.

MSVC takes into account alignment attributes on typedefs when
determining whether or not a field has a certain required alignment.

Do the same in clang by tracking whether or not we saw such an attribute
when calculating the type's bitwidth and alignment.

This fixes PR20418.

Reviewers: rnk

Differential Revision: http://reviews.llvm.org/D4714

llvm-svn: 214274

1 files changed, 13 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index b5205b3e623..0ebc5838d2f 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -2107,7 +2107,12 @@ static bool matchTypes(ASTContext &Context, Sema::MethodMatchStrategy strategy,
   // validate the basic, low-level compatibility of the two types.
 
   // As a minimum, require the sizes and alignments to match.
-  if (Context.getTypeInfo(left) != Context.getTypeInfo(right))
+  TypeInfo LeftTI = Context.getTypeInfo(left);
+  TypeInfo RightTI = Context.getTypeInfo(right);
+  if (LeftTI.Width != RightTI.Width)
+    return false;
+
+  if (LeftTI.Align != RightTI.Align)
     return false;
 
   // Consider all the kinds of non-dependent canonical types:
@@ -2159,7 +2164,13 @@ static bool tryMatchRecordTypes(ASTContext &Context,
     return false;
 
   // Require size and alignment to match.
-  if (Context.getTypeInfo(lt) != Context.getTypeInfo(rt)) return false;
+  TypeInfo LeftTI = Context.getTypeInfo(lt);
+  TypeInfo RightTI = Context.getTypeInfo(rt);
+  if (LeftTI.Width != RightTI.Width)
+    return false;
+
+  if (LeftTI.Align != RightTI.Align)
+    return false;
 
   // Require fields to match.
   RecordDecl::field_iterator li = left->field_begin(), le = left->field_end();